Vibrational Ground-State SiO [ITAL]J[/ITAL] = 1–0 Emission in Orion IRc2 Imaged with the VLA

Abstract

We have used the VLA to observe SiO(v = 0, J = 1-0) at 43.4 GHz in the IRc2 region of Orion with 2'' resolution. Both a thermal component and a maser component are detected, making IRc2 the only known star-forming region with an SiO vibrational ground-state maser. The maser emission is double peaked and is extended over ~900 AU with the same position angle as that observed for the v = 1 masers. The velocity extent of the v = 0 masers (30 km s-1) is similar to the v = 1 SiO, OH, and H2O masers; we suggest that their motions are dominated by the outflow from IRc2 rather than a rotating disk. The gradient in the thermal component is in the same sense as the CO outflow from IRc2 and appears to trace the interaction region between the IRc2 wind and nearby dense molecular material to the south. The thermal SiO emission is clearly centered on IRc2 and not the hot core.